I have a project coming up that will require me to interface Freeswitch to some rather arcane legacy T1 protocols.  Specifically digital loop start, and station-side digital loop start.  I'm concerned that the userland support for these may be incomplete or even non-existent in FreeTDM.  

I've successfully used FreeTDM to connect to PRI, but when I look for span configuration options for CAS T1, the only things that I see that may be applicable are described as "analog" options, and that doesn't sound quite right for loop start on T1 channels (but I could be wrong about that).  If I were to use Asterisk for this, I would configure chan_dahdi.conf for "signalling=fxs_ls" and/or "signalling=fxo_ls".